We just went to IOA the first week of January and only had a 1 day pass. We were there for WWOHP and it was amazing. The crowds were crazy, but I day was enough.
Here is what we did:
We arrived when the park opened to the public at 9 am, our wait for Forbidden journey was about 90 minutes.

I got to ride again because we had a 2 year old and my DH stayed with him on the first round and our friends stayed with DS2, and the other kids while we rode again. They only allowed 1 person to ride for the swap - we couldn't decide which kid so I went again

. When we got out it was 120 minute wait and stayed there most of the day.
We had to wait 60 minutes for Flight of the Hippogriff but only 10 minutes for Dueling Dragons. Olivanders was packed so we didn't attempt (the line was much shorter in the evening). The butterbeer lines were outrageous. It is great that you can get soda refills on your mug for around $1. I wasn't a big fan of the butterbeer. We did not get the frozen though and I heard it is better.
After WWHOP, we went to Seuss Landing. High in the Sky Trolley was an hour wait - we waited. The other rides only had 5 to 25 minute waits. We did the carousel and the play area. Some in our group went to Hulk (about 1 hour wait) during this time.
After Seuss landing we went to Jurassic Park. Don't do the River Adventure if it is cold - big mistake - love the ride though. Then we waited 1 hour for the Pteredon flyers - never again. After that we went back to Forbidden Journey and some of us did the single rider line. It took us 30 minutes - Regular standby said 70 minutes. It was great seeing Hogsmeade at night.
We rode the Cat in The Hat ride on the way out. We left about 7:30 pm (30 minutes before the park closed) and grabbed KFC on the way back to the resort.
We never did full service to eat during the day, we just ate at kiosks/walkup if we saw a short line and we were hungry. We had time for some shopping. We toured with 10 people total. We didn't get to everything but 1 day was enough. With less people you could probably do a lot more.